Temporary protective coatings are widely used to protect the surfaces of various products, parts, or components during manufacture, assembly, shipping, installation, or refinishing operations. The temporary protective coatings are used to prevent damage from scratching, nicking, pitting, staining, corrosion, sticking, or discoloration. The protective coatings are also used to simplify or enhance cleaning operations whereby surface contamination is eliminated by removal of the temporary coating. Temporary coatings or “maskings” are also used during painting or refinishing operations of automobiles, for example, to prevent application of paint to areas not intended to be painted, and to prevent damage from paint overspray. Temporary protective coatings are also used during the transportation of various articles from a manufacturing site to a retail location. The surface finishes of new vehicles such as automobiles or boats must often be protected from abrasive particles or other deleterious conditions in the environment during shipment by road, rail, or sea.
Other products or articles that may be protected by temporary removable coatings include those with precision or high gloss surfaces such as mirrors, windows, optical lenses, plastics such as Plexiglas™, plastic laminates such as Formica™, composites such as Corian™ countertops, appliances, metal tools, parts, and machinery, and kitchen and bathroom fixtures such as sinks, bathtubs, and plumbing fixtures.
Temporary removable coatings may also be applied to various surfaces such as floors, countertops, showerstalls, appliances, and the like which tend to become contaminated with dirt, oil, or grease through normal use. In these applications, the temporary protective coating on the surface will become contaminated or dirty, and removal of the temporary protective coating eliminates the contamination, thereby greatly simplifying cleaning of the surface.
A number of approaches that utilize the application of a liquid solution or dispersion temporary protective coating composition have been described.
U.S. Pat. No. 4,341,687 describes a peelable, film forming paint comprising a mixture of an isocyanate functional prepolymer, a polyurethane resin, and ethylene glycol monoalkyl ether in a volatile organic solvent. The paint is useful for removing contamination from and protecting surfaces subject to contamination. No aqueous dispersions are disclosed.
There has been a move in recent years to avoid the use of volatile organic solvents (VOCs). Volatile organic solvents are often flammable and hazardous from a health and safety perspective. They are subject to increasingly stringent environmental regulations due to emission and disposal concerns. For these reasons, much effort has been expended in replacing organic solvent based adhesives, coatings, and sealers, for example, with water based systems.
U.S. Pat. No. 6,124,044 describes the use of aqueous emulsions of vinyl-acrylic copolymers and vinyl acetate ethylene emulsions to form barrier films on applied surfaces, the film being removable by peeling from the surface. The emulsion is said to be useful for protecting the exterior surfaces of automobiles and other products from damage.
U.S. Pat. No. 5,494,702 describes solvent-free aqueous based compositions for protecting surfaces from paint in painting operations. The compositions comprise polyvinyl alcohol, a plasticizer, and a surfactant in water. After the painting operation, the protective composition is removed by washing with a pressurized stream of water or by scrubbing.
Other compositions for protecting surfaces during painting operations and that are removed by washing with water have been described. U.S. Pat. No. 5,308,647 describes compositions comprising film forming thickeners, surfactants, and polyglycerols in water.
U.S. Pat. No. 6,117,485 describes the use of compositions comprising dextrin, a plasticizer, and water for temporary masking operations. No peelable coatings are disclosed.
U.S. Pat. Nos. 5,081,174, 5,639,814 and 6,187,849 B1 describe weldable, protective coatings for use on metal. The coatings comprise neutralized acrylic polymers and wax lubricants. The coatings are removed by washing with an aqueous acid or alkaline cleaning solution.
U.S. Pat. No. 5,945,462 describes the use of aqueous based compositions comprising polymerizable acrylic functional urethane prepolymer resins containing a photoinitiator and a release agent which are irradiated with UV radiation to photocrosslink the prepolymer resins to form strippable, protective coatings. The release agents include lecithin, polyethylene glycols, and fatty acids.
Canadian Patent Application CA 2,314,523 describes strippable coating compositions for temporary protection purposes. The compositions comprise at least two different aqueous anionic dispersions of polyurethane polyureas wherein the films resulting from drying the dispersions have glass transition temperatures in the range of −30° C. to −45° C. The coating composition is stated to be co-solvent free.
U.S. Pat. Nos. 5,965,195 and 6,172,126 B1 describe strippable coating compositions comprising organic solvent-free aqueous, anionic dispersions of polyurethane polyureas derived from a prepolymer prepared from diisocyanates, polyols, a 2,2-bis(hydroxymethyl)alkane monocarboxylic acid, a monofunctional chain terminating agent, water, and a neutralizing agent, with the specific provisions that the NCO content of the prepolymer is up to 25% lower than the theoretical value. The entire synthesis is performed in the homogeneous phase, and no solvent having a boiling range of greater than 100° C. is used during the preparation of the dispersion. The coating composition is stated to be co-solvent free.